<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    :root {
      --simplecolor: red;
      font-size: 20px;
    }

    p {
      font-size: 18px;
      /* zoom: 0.5; */
      /* transform: scale(0.5); */
      color: var(--simplecolor);
    }
  </style>
</head>

<body>
  <p>你好</p>
</body>

</html>